MIPS: N32: Use compat getsockopt syscall

The IP_PKTOPTIONS sockopt puts control messages in option_values, these
need to be handled differently in the compat case. This is already done
through the MSG_CMSG_COMPAT flag, we just need to use
compat_sys_getsockopt which sets that flag.

Signed-off-by: Sorin Dumitru <sdumitru@ixiacom.com>
Reviewed-by: James Hogan <james.hogan@imgtec.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/7115/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>